This project is being pursued with three major goals in mind: (1) A histopathologic and correlative study of the changes occurring when normal ocular tissue becomes malignant; (2) investigation of the possible role of viruses in intraocular tumors; and (3) investigation of specific morphologic and biochemical changes resulting from transformation of ocular tissue by oncogenic viruses. During the past year a study of infection of neonatal pups with canine herpes virus resulted in widespread development of retinal dysplasia but no instance of intraocular tumor. Infection of fetal and neonatal kittens with feline sarcoma virus did result in a retinal tumor with morphologic similarities to retinoblastoma. Existing human retinoblastoma cell lines were maintained and expanded. Human cases of ocular-related alignancy were studied in detail.